01931 Glass transition and thermal stability of hard magnetic bulk NdAIFeCo metallic glass

12 Refractories/ceramics power plant technological and optimized configuration, a net efficiency of -58% is conceivable for the HAT cycle. Various options of coal fuelled HAT cycles based on the integrated gasification humid air turbine concept are analysed and compared. In the gasification process, the entrained flow gasifiers both with coal dry-feeding and wet-feeding systems are considered to incorporate with HAT cycles. The options focus on different ways of using the thermal enthalpy produced in the gas island either by generating steam or by preheating water for heat recovery. At the gas turbine inlet temperature of 1250”, the cycle applying gas turbine blade cooling with steam in open loop can reach a net efficiency of 50.6%. If a hot gas cleaning device is used instead of the conventional wet gas cleaning device in gas the island, a further increase of 0.6% is predicted. Another possibility for the coal fuelled HAT cycle is based on the available PFBC plant. In this configuration, a topping carbonizer is applied for the coal partial gasification, where syngas is generated and then delivered to the gas turbine combustion chamber for combustion. Furthermore, the steam turbine is removed in this cycle, and the steam produced in the fluidized bed boiler is used for cooling the gas turbine blade in an open loop. At the gas turbine inlet temperature of 1250”, a net efficiency of 50.8% is achievable for this cycle. To further improve the HAT cycles efficiency, besides further possibly elevating the gas turbine inlet temperature, a combination with solid oxide fuel cell as topping cycle is suggested. By using natural gas as fuel, a cycle efficiency of >70.0% can be expected. It is an effective alternative of the so-called fuel cell-gas turbine hybrid cycles. The thermodynamic performance of the HAT cycles involved are competitive in comparison to the other modern power plant systems. 03/01927 Use of alternative fuels in the Polish cement industry Mokrzycki, E. er al. Applied Energy, 2003, 74, (l-2) 10 l-l 1 I. Alternative fuels are made up of mixtures of industrial, municipal and hazardous wastes. These fuels need to have an appropriate chemical energy content which depends on the type of components and their organic content. An industry that is particularly well suited to using alternative fuels is the cement industry. There are a number of factors that promote the use of alternative fuels in cement kilns. Of these factors, the most notable are: the high temperatures developed, the appropriate kiln length, the long period of time the fuel stays inside the kiln and the alkaline environment inside the kiln. There are a number of countries that use their own alternative fuels in cement plants. These fuels have different trade names and they differ in the amounts and the quality of the selected municipal and industrial waste fractions used. The fuels used should fall within the extreme values of parameters such as: minimum heating value, maximum humidity content, and maximum content of heavy and toxic metals. Cement plants in Poland also use alternative fuels. The Lafarge Group has initiated activities directed at promoting the wider use of alternative fuels. There are a number of wastes that can be incinerated as fuel in cement plants. Some that can be mentioned are: selected combustible fractions of municipal wastes, liquid crude-oil derived wastes, car tyres, waste products derived from paint and varnish production, expired medicines from the pharmaceutical industry and others. The experience gained by the cement plants of Lafarge confirms that such activities are economically and ecologically beneficial. The incineration of alternative fuels in cement plants is a safe method for the utilization of waste that is ecologically friendly and profitable for the industrial plants and society alike.

12 REFRACTORIES/ CERAMICS Properties, production, applications 03/01928 Back electrode formation for pol -Si thin film solar cells on glass having AIC-grown see J fng layer Widenborg, P. et al. Solar Energy Materials and Solar Cells, 2002, 74. (l-4), 305-314. Various conductive materials (Al, MO and TiN) were deposited onto glass substrates to evaluate whether poly-Si seed layers can be formed on such substrates by means of Al-induced crystallization (AIC) of a-Si at low temperature around 450°C. The material located between the glass and the poly-Si film serves as the back electrode of a substratetype thin-film solar cell configuration. The outcome of the investigation is that MO is found to be not compatible with the AIC process. In contrast, Al and TIN showed moderate to good compatibility. TiN is

the has high the

only viable satisfactory resistivity near-infrared

(properties, production, appliCatiOnS)

choice for high-temperature applications (>54o”C). Al back electrode properties whereas TIN has a medium (120 uR cm) and an estimated low back reflectance at wavelengths critical for light trapping.

03/01929 Carbon-ceramic composites from coal tar pitch and clays: application as electrocatalyst support Montilla, F. et al. Carbon, 2002, 40, (12), 2193-2200. Carbon-ceramic composites have been prepared and characterized by different techniques (electron microscopy, X-ray microanalysis, X-ray diffraction and cyclic voltammetry). The effect on the conductivity of the thermal treatment temperature of the composites and the structure of the starting ceramic has been analysed. The results demonstrate that the layered structure of the clay determines their conductivity. The composites prepared are conductors and the conductivity goes through a maximum with increasing thermal treatment. Platinum has been successfully deposited on the carbon-ceramic composite by chemical and electrochemical methods. A better distribution of platinum and smaller particle sizes are obtained by the electrochemical method. The direct electrooxidation of methanol in acid medium has been studied on platinum-modified carbon-ceramic electrodes. 03/01930 Foamed glass-ceramic materials based shale by-products Gorokhovsky, A. V. et al. Glass Science und Technology Main,

Germany),

2002,

on oil (Frankjkrt/

75. (5). 259.-262.

The feasibility and features of the production of foamed glass-ceramic materials based on oil shale ash were investigated. The optimal regime of synthesis found involved the following steps: glass fusion at 14Oo”C, preparation of the glass powders and blending with the foaming agent. The foaming was carried out at 900 to 920°C with a further one-stage crystallization at 790 to 820°C. It was noted that the admixture of calcium carbonate, as a foaming agent, changed the phase composition of the resulting glass-ceramics by an increased rate of the crystallization process and the intensive formation of gehlenite simultaneously with diopside. 03/01931 Glass transition magnetic bulk NdAlFeCo Wei, B. C. et al. Materials

and thermal metallic glass

stability

Science & Engineering, Microstructure and Processing,

of hard A: 2002.

Structural

(l?), 307-3 I 1. Glass transition and thermal stability of bulk Nd60A110Fe20-COio metallic glass were investigated by dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry (DSC), x-ray diffraction (x-ray diffraction) and scanning electronic microscopy (SEM). The glass transition temperature, not revealed by DSC, is alternatively detected by DMTA via storage modulus E’ and loss modulus E” measurement to be 498 K at a heating rate of 0.167 K/s. The calculated reduced glass transition temperature (TsiT,) is 0.63. The large value of T,/T, of this alloy is consistent with Its good glassforming ability. The crystallization process of the metallic glass is concluded as follows: amorphous amorphous+metastable FeNdAl phase amorphous+primary &FeN-dAl phase primary Gphase+eutectic h-pbase+Nd,Al+Nd,Co. The appearance of hard magnetism in this alloy is ascribed to the presence of amorphous phase with highly relaxed structure. The hard magnetism disappeared after the eutectic crystallization of the amorphous phase.

Materials.

Properties.

A334,

03/01932 Incorporation of fibres in geothermal well cements Berndt, M. L. and Philippacopoulos, A. J. Geothermics. 2002, 31, (6) 643-656. Fibre-reinforced cements are of potential value in geothermal well cementing jobs due to their ability to withstand higher tensile stresses than conventional cements. Screening tests were performed to evaluate different fibre types with the objective of identifying systems offering the greatest improvement in cement tensile strength. The fibres investigated included steel, stainless steel, carbon, basalt and glass. The baseline cement matrix was standard Class G cement/40% silica flour and variations on this were latex-modification and lightweight formulations incorporating either perlite or microspheres. The fibres that showed the best performance at low volume fraction were 13 mm brass-coated round steel fibres. Steel and carbon microfibres also improved the tensile strength provided the volume fraction was high enough. Thermal and hydraulic properties of cements reinforced with steel fibres were measured and compared with unreinforced mixes. Based on the results, selected fibre types will be used in further property characterization studies and engineering analysis of geothermal wells completed with fibre-reinforced materials. 03101933 Influence of mineral precipitation and dissolution on hydrologic properties of porous media in static and dynamic systems Freedman, V. L. et al. Applied Geochemistry, 2003, 18, (4). 589-606. Fuel

and

Energy

Abstracts

September

2003

323